In general, an optical fiber connector having a splice assembly therein for optically connecting end surfaces of plain fiber portions, from each of which has been removed a cover of the optical fiber cable, while abutting the end surfaces to each other, has been conveniently used at a work-site for easily connecting optical fiber cables to each other, as disclosed in Japanese Patent No. 3445479.
Japanese Patent No. 3445479 discloses a so-called mechanical-splice-type optical fiber connector comprising a splice assembly for holding a ferrule having a primary coating portion and an extension of the primary coating portion leading out from a rear end surface of the ferrule, wherein a primary coating portion of an optical fiber cable is guided into the splice assembly from an end thereof so that end surfaces of the plain fiber portions are abutted to each other and optically connected to each other.
Such an optical fiber connector is used, for example, when a domestic data communication service is provided through optical fibers, and is stored in an optical communication junction box of a predetermined size provided on a telephone pole or in a residence. The optical communication junction box also has optical fiber cables and optical devices other than the optical fiber connector. On a side of the optical fiber connector from which the optical fiber is led out, the optical fiber cable may be guided via a boot member for avoiding abrupt bending of the optical fiber cable.
As optical fiber data communication services have become popular, the number of optical devices used therefor has increased, whereby the vacant space within the optical communication junction box has been reduced. Accordingly, it is desired to miniaturize the optical fiber connector to be accommodated in the optical communication junction box. When the boot member is mounted to a wall of the optical fiber connector, however, there is a problem in that a side of the optical fiber connector from which the optical fiber leads out is protruded to substantially enlarge the size of the optical fiber connector, which again reduces vacant space available within the box. To solve such a problem, a countermeasure has been demanded wherein the optical fiber can be bent within the connector and without using the boot member.
On the other hand, a proposal has been made wherein the primary coating portion is covered solely with a thin inner coating to increase the vacant space within the box because it would be unnecessary to cover the outer circumference of the primary coating portion with a thick coating of, for example, polyethylene, within the optical communication junction box. In this case, the primary coating portion with, for example, a diameter of 0.25 mm suitably has a multi-layered structure covered with a thin coating for the purpose of facilitating handling and/or visibility.
FIG. 5 illustrates one example of the prior arts cited as a comparison with the present invention. In the drawing, when a splice assembly 33 stored within an optical fiber connector 30 corresponds to a primary coating portion of 0.25 mm diameter, an outer coating of the primary coating portion 31 having a diameter larger than 0.25 mm is removed by using a skin peeling tool, or another tool, until the diameter becomes 0.25 mm. A boundary 32, at which the diameter of the primary coating portion 31 changes, is protected within the interior of the optical fiber connector 30.
However, as the boundary 32 of the optical fiber core 31 has a step at which the diameter changes, there is a risk in that stress is concentrated at the boundary 32 if the primary coating portion 31 is bent within the interior of the connector 30, resulting in a bending loss of optical signal or breakage of the primary coating portion.